<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    :root {
      --mian-font: sans-serif;
      font-size: calc(.5em + 1vw);
    }

    .box {
      /* width: 90vmin; */
      width: 100vmin;
      height: 50vmin;
      background-color: antiquewhite;
    }

    body {
      line-height: 1.2;
      font-family: var(--mian-font);
    }

    .text {
      font-size: 2em;
    }
  </style>
</head>

<body>

  <div class="box">
    hello
  </div>
</body>

</html>